Revenue from contracts with customers - Summary of the Revenue recognized that Relates to Carried-Forward Contract Liabilities (Detail) - EUR (€) € in Thousands  | 
12 Months Ended | ||
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Dec. 31, 2021  | 
Dec. 31, 2020  | 
Dec. 31, 2019  | 
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| Revenue recognized that was included in the contract liability balance at the beginning of the period | € 7,280 | € 5,250 | € 3,715 | 
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- Definition Text block. No definition available. 
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- Definition The amount of revenue that was included in the contract liability balance at the beginning of the period. [Refer: Contract liabilities; Revenue from contracts with customers] Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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